There is a memory device as a media for storing data. Some memory devices contain a nonvolatile semiconductor memory and a controller for controlling it. An example of such a memory device may be a memory card such as an SD™ card. Such a memory card and a host device record (or, write) and play (or, read) content data in compliance with schemes for protecting the copyright of the data. Several functions are defined for such schemes; however, some of them may not be fully in use due to their natures. Specifically, practicing some functions require specific procedure and operation by a user; however he or she may be hardly willing to do such procedure and operation because protection of content data provides merits to content holders but not to the user.